media: atmel: atmel-sama5d2-isc: fix warning in configs without OF

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> drivers/media/platform/atmel/atmel-sama5d2-isc.c:323:34: warning: unused variable 'atmel_isc_of_match' [-Wunused-const-variable]
static const struct of_device_id atmel_isc_of_match[] = {
^
1 warning generated.

vim +/atmel_isc_of_match +323 drivers/media/platform/atmel/atmel-sama5d2-isc.c

   322
 > 323  static const struct of_device_id atmel_isc_of_match[] = {
   324          { .compatible = "atmel,sama5d2-isc" },
   325          { }
   326  };
   327  MODULE_DEVICE_TABLE(of, atmel_isc_of_match);
   328

Fixed warning by guarding the atmel_isc_of_match by CONFIG_OF.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>